J3/03-216
Date: 04 August 2003
To: J3
From: Aleksandar Donev
Subject: Response to N1558 on Nagging Doubts
Re: WG5/N1559
ISO/IEC JTC1/SC22/WG5/N1559
From: Aleksandar Donev
Subject: Response to N1558 27 Jul 2003
Here are some comments to Kurt's complaints (most of which I have heard before in one form or another in various discussions):
> ====================================
> Nagging Doubt II: Type Compatibility
> ====================================
I'll leave this one to Malcolm...
> =======================================================
> Nagging Doubt III: The "Value" of a Derived-Type Object
> =======================================================
> CALL SUB(X,(X))
> How is a processor supposed to preserve this
> part of the value for the duration of SUB's execution?
It cannot, so maybe the text that requires that should be modified instead.
Something like the value at the *beginning* of the execution...
> I suggest that for derived-types, we can give rules for
> enumerating the possible representations that type could have,
> but that enumeration is not the same thing as an enumeration of
> the values of that type.
If you look at my paper which made this "clarification of VALUE", you will see that I also agree that "value of" is not something the standard can really define because it depends on what the derived type actually represents (i.e. the abstraction), but it is not possible to fix this in Fortran now (or maybe ever). The edits merely try to patch the very *inadequate* definition of value of in the previous draft which did not at all say anything about the distinction between ordinary, pointer and allocatable components. The edits were not meant to provide a great new definition of "value of", as I do not know how to do that. At least implementors can implement the present text.
And the user who does your CALL SUB(X,(X)) and expects miracles will simply be reminded not to expect miracles from computers :-(
Best,
Aleksandar
--
NOTE change of primary e-mail to adonev@math.princeton.edu
__________________________________
Aleksandar Donev
Complex Materials Theory Group (http://cherrypit.princeton.edu/)
Princeton Materials Institute &
Program in Applied and Computational Mathematics
@ Princeton University
Address:
419 Bowen Hall, 70 Prospect Avenue
Princeton University
Princeton, NJ 08540-5211
E-mail: adonev@math.princeton.edu
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__________________________________